1. Field of the Invention
The present disclosure relates to a fuel cell.
2. Discussion of the Background
A solid polymer electrolyte fuel cell, for example, includes unit cells. Each of the unit cells includes a membrane electrode assembly (MEA) and a pair of separators sandwiching the MEA therebetween. The MEA includes an electrolyte membrane, which is a polymer ion-exchange membrane, and an anode electrode and a cathode electrode sandwiching the electrolyte membrane therebetween. The solid polymer electrolyte fuel cell, which usually includes a certain number of unit cells that are stacked together, is used as a fuel cell stack for an electric vehicle.
In the fuel cell, a fuel gas channel (reactant gas channel) for supplying a fuel gas to the anode electrode is formed on a surface of one of the separators, and an oxidant gas channel (reactant gas channel) for supplying an oxidant gas to the cathode electrode is formed on a surface of the other of the separators. Moreover, a coolant channel, through which coolant flows, extends along surfaces of the separators of the unit cells that are adjacent to each other.
Some fuel cells have a so-called internal manifold structure. The internal manifold structure is built up of a reactant gas inlet manifold, a reactant gas outlet manifold, a coolant inlet manifold, and a coolant outlet manifold. These manifolds are disposed in the fuel cell and extend through the fuel cell in the stacking direction of the separators. In the fuel cell stack, it is necessary to uniformly supply a reactant gas to a plurality of reactant gas channel of each separator.
Japanese Unexamined Patent Application Publication No. 10-172594, for example, describes a fuel cell that addresses this problem. The fuel cell is formed by stacking a separator 1 as illustrated in FIG. 5 and a unit cell (not shown) on top of the other. The unit cell includes an air electrode, a fuel electrode, and a solid electrolyte layer sandwiched between these electrodes. A gas supply hole 1a and a gas outlet hole 1b are formed in opposite corners of the separator 1, and a plurality of gas distribution grooves 1c are formed in a surface of the separator 1.
One or both of a gas flow regulating portion 2 and an obstacle 3 is formed in one or both of a gas inlet portion and a gas outlet portion of the separator 1, and/or the depth of the gas distribution grooves 1c is made to be less than the depths of other parts of the grooves, and thereby a pressure dropping function is provided.
The fuel cell is configured to uniformly distribute the gas by increasing the pressure drop through the gas inlet portion, the gas outlet portion, and the gas distribution grooves 1c. 